Strength in Numbers: Threshold ECDSA to Protect Keys in the Cloud.
Marc Green, Thomas Eisenbarth · 2015
Abstract. Side-channel attacks utilize information leakage in the imple-mentation of an otherwise secure cryptographic algorithm to extract se-cret information. For example, adversaries can extract the secret key used in a cryptographic algorithm by observing cache-timing data. Threshold cryptography enables the division of private keys into shares, distributed among several nodes; the knowledge of a subset of shares does not leak in-formation about the private key, thereby defending against memory dis-closure and side-channel attacks. This work shows that applying thresh-old cryptography to ECDSA—the elliptic curve variant of DSA—yields a fully distributive signature protocol that does not feature a single point of failure. Our security analysis shows that Threshold ECDSA protects against a wide range of side-channel attacks, including cache attacks, and counteracts memory disclosure attacks. We further provide the first per-formance analysis of Threshold ECDSA, and provide a proof of concept of the protocol in practice.